You're thinking of "Tomorrow is Yesterday" instead of Mr. Atoz and the Atavachron.
Ooops! You're right!

I think I jumped to that because "All of Our Yesterdays" WAS SUCH A GOOD EP!!! My mind could not process that anyone would hate that ep, so I read it wrong.

"SUCH A GOOD EP"? Aaaaaauuuugh! I hate it so, so, so much. I hate the hackneyed plot; I hate the fact that instead of using something approximating a real Indian tribe, they once again use Generic Indian Tribe #101 (I know this was only the '60s, but it's still not right); I hate the costumes (Kirk looks, I'm sorry, like a dork in that headband - and why does his hair never grow any longer than the regulation Fed haircut?); I hate the embarassing dialog; I hate how pissy and petulant McCoy acts in this one; I hate how after all this happens, Kirk forgets about his beloved wife (and child, even - she was pregnant, if I remember correctly) almost before the Enterprise leaves orbit; I hate...just about everything, really. Well, the girl who plays Kirk's wife is lovely, in spite of that ridiculous wig, as is the scenery, but I truly loathe this episode.
We had a thread on this a few months back, and opinion was definitely split, so while you can find other people who like this episode,
Chris, you can find plenty of other haters, too. Neither of us is alone. Isn't that nice?